Enabling Replication Between Clusters with Kerberos Authentication

When using BDR with Kerberos authentication enabled, BDR requires all the ports listed on the following page: Port Requirements for Backup and Disaster Recovery.

Additionally, the port used for the Kerberos KDC Server and KRB5 services must be open to all hosts on the destination cluster. By default, this is port 88.

1. On the hosts in the destination cluster, ensure that the krb5.conf file (typically located at /etc/kbr5.conf) on each host has the following information:
   • The KDC information for the source cluster's Kerberos realm. For example:

     [realms]
      SRC.EXAMPLE.COM = {
       kdc = kdc01.src.example.com:88
       admin_server = kdc01.example.com:749
       default_domain = src.example.com
      }
      DST.EXAMPLE.COM = {
       kdc = kdc01.dst.example.com:88
       admin_server = kdc01.dst.example.com:749
       default_domain = dst.example.com
      }

   • Realm mapping for the source cluster domain. You configure these mappings in the [domain_realm] section. For example:

     [domain_realm]
      .dst.example.com = DST.EXAMPLE.COM
      dst.example.com = DST.EXAMPLE.COM
      .src.example.com = SRC.EXAMPLE.COM
      src.example.com = SRC.EXAMPLE.COM

2. On the destination cluster, use Cloudera Manager to add the realm of the source cluster to the Trusted Kerberos Realms configuration property:
   1. Go to the HDFS service.
   2. Click the Configuration tab.
   3. In the search field type Trusted Kerberos to find the Trusted Kerberos Realms property.
   4. Click the plus sign icon, and then enter the source cluster realm.
   5. Click Save Changes to commit the changes.
3. Go to Administration > Settings.
4. In the search field, type domain name.
5. In the Domain Name(s) field, enter any domain or host names you want to map to the destination cluster KDC. Use the plus sign icon to add as many entries as you need. The entries in this property are used to generate the domain_realm section in krb5.conf.
6. If domain_realm is configured in the Advanced Configuration Snippet (Safety Valve) for remaining krb5.conf, remove the entries for it.
7. Click Save Changes to commit the changes.

1. Perform the procedure described in the previous section.
2. On the hosts in the source cluster, ensure that the krb5.conf file on each host has the following information:
   • The kdc information for the destination cluster's Kerberos realm.
   • Domain/host-to-realm mapping for the destination cluster NameNode hosts.
3. On the source cluster, use Cloudera Manager to add the realm of the destination cluster to the Trusted Kerberos Realms configuration property.
   1. Go to the HDFS service.
   2. Click the Configuration tab.
   3. In the search field type "Trusted Kerberos" to find the Trusted Kerberos Realms property.
   4. Enter the destination cluster realm.
   5. Click Save Changes to commit the changes.

   It is not necessary to restart any services on the source cluster.

As part of Test Connectivity, Cloudera Manager tests for properly configured Kerberos authentication on the source and destination clusters that run the replication. Test Connectivity runs automatically when you add a peer for replication, or you can manually initiate Test Connectivity from the Actions menu.

This feature is available when the source and destination clusters run Cloudera Manager 5.12 or later. You can disable the Kerberos connectivity test by setting feature_flag_test_kerberos_connectivity to false with the Cloudera Manager API: api/<version>/cm/config.

If the test detects any issues with the Kerberos configuration, Cloudera Manager provides resolution steps based on whether Cloudera Manager manages the Kerberos configuration file.

Kerberos Recommendations

If Cloudera Manager manages the Kerberos configuration file, Cloudera Manager configures Kerberos correctly for you and then provides the set of commands that you must manually run to finish configuring the clusters. The following screen shots show the prompts that Cloudera Manager provides in cases of improper configuration:

Configuration changes:

Steps to complete configuration:

If Cloudera Manager does not manage the Kerberos configuration file, Cloudera manager provides the manual steps required to correct the issue. For example, the following screen shot shows the steps required to properly configure Kerberos: